To an increasing extent, electronic components are moving into areas that had long been considered to fall into the realm of mechanics. This also relates in particular to the machine and automobile industry, which equip their products, corresponding to the general trend, with electronics to electronically detect, control, and regulate mechanical functions and/or communicate information to a user. Sensor arrangements and actuators can serve as connecting links between the two worlds to convert the mechanical functions of a component into electronically processible signals and vice versa.
Position sensors can be used to detect the position or the state of movement of a mechanical component. The information that is detected by the position sensor can be converted into electrical signals that change based on the change in position of the component. Position sensors can be an important component in many mechanical products that first enables an intelligent control.
The detection of a path of a component covered along a predefined path is useful, for example, when cutting materials into lengths. The analogous translatory position sensors used for this purpose can work according to Ohm's principle or the induction principle. In both principles, the analog (continuous) conversion of a path into an electrical signal is used. In position sensors based on the ohmic measuring principle, the electrical voltage, whose value depends on the wire length, is scanned by a resistance wire via a slider. Such potentiometers can have the drawback that the slider and the wire are subjected to wear. By the induction principle, a magnetic field, which produces an electric voltage in a coil, is induced in the measuring system via AC voltage. The coil is moved relative to the other measuring system. The voltage induced in the coil depends on its position in the measuring system. Using suitable electronic circuits, a positional measuring signal can be obtained therefrom. The measuring method is contact-free but, an AC voltage source is used and a relatively large electronic expense is used to produce a position measuring signal.
Other known path measuring systems use, for example, magnetic tapes, whose magnetic field is scanned by a read head and is converted into a position measuring signal or path measuring signal. With a wire length sensor, a wire is wound onto a drum or is run on a roller corresponding to the path. The revolutions can be detected and a path measuring signal is produced therefrom. With the magnetostrictive principle, a movable magnet changes its sound reflection properties. With an ultrasound-transit time measurement, the site of the magnet and thus the movement path can be determined in connection with a relatively expensive electronic analysis device.
U.S. Pat. No. 6,753,680 B2 discloses a position sensor that includes two flow conductor rails that run parallel and some distance apart to one another and permanent magnets that are arranged on the ends of the flow conductor rails. A Hall sensor that can be moved relative to the longitudinal extension of the flow conductor rails is arranged in the gap between the flow conductor rails. The output signal that is present at the output of the Hall sensor, which changes subsequent to the relative movement, is further processed and can be used as a measure of the distance covered by the monitored component. Because the sensor is run between rails and the flux density in the mean range is relatively small, the structure can be sensitive to disruption by external magnetic fields and positional tolerances of the sensor.
Known systems that are based on, for example, sliding gauges, operate incrementally, i.e., information on the absolute position of the moved component is available only if it is determined before the measurement of a zero point position, corresponding to a basic output signal, of the sensor. If, for example, in the case of a seat adjustment, first the seat is adjusted before the engine and thus the automobile electrical and electronic systems are put into operation, it is difficult with the known position sensors to determine the exact position of the seat. Moreover, the known magnetic position sensors depend on the amplitude of the detected magnetic field. The effect of this can be that, for example, the Hall sensor has to be adjusted very exactly relative to the flow conductor rails. Inaccuracies in the adjustment or vibration-caused adjustments can have a direct negative effect on the measuring results.
From WO 2004/015375 A1, a magnetoresistive linear position sensor is known that operates based on magnetoresistive detectors, which can be arranged in such a way that they form at least two Wheatstone bridges that have a common center and are twisted relative to one another. Using the two Wheatstone bridges, from the scanned bridge voltages of the two Wheatstone bridges, which change with the translatory passing movements of a bar magnet or a magnet arrangement that is arranged at a certain distance, the direction of the magnetic flux density can be derived. For a bar magnet that is magnetized in the translational direction, sinusoidal plots of the flux density can be produced from a pole of the magnet. From the superposition of sinusoidal plots measured from the two Wheatstone bridges, an essentially linear connection can be produced between the movement path of the bar magnet and the change of the angle of the vector of the magnetic flux density. Thus, from the direction of the vector of the magnetic flux density, the length of the movement path can be derived. The sensitivity of the sensor depends on the length of the bar magnet or on the total length of the magnetic arrangement and on the magnetic pole shape. Also, the magnet(s) should be arranged at a very specifically defined distance to the arrangement of the two Wheatstone bridges. The magnetic field strength should be large enough so that the individual magnetoresistive detectors are found in the saturation state in order to prevent the resistance of the magnetoresistive detectors from changing based on the amount of the magnetic flux density and to prevent the measuring results from changing. These known linear position sensors include a number of magnetoresistive detectors that are assembled into at least two Wheatstone bridges that are twisted toward one another, and a magnet arrangement that is relatively complex and involves a relatively large expenditure for the adjustment of the components to one another.